Structure of exhaust chamber in gas turbines



P 10, 1968 HIDEO KOJIMA 3,400,911

STRUCTURE OF EXHAUST CHAMBER IN GAS TURBINES Original Filed Oct. 18, 1966 INVENTOR BY Q/Mi.

ATTORNEY United States Patent 3,400,911 STRUCTURE OF EXHAUST CHAMBER IN GAS TURBINES Hideo Kojima, Hitachi-shi, Japan, assignor to Hitachi, Ltd., Tokyo, Japan, a corporation of Japan Continuation of application Ser. No. 587,496, Oct. 18, 1966. This application Dec. 4, 1967, Ser. No. 691,102 Claims. (Cl. 253--39) ABSTRACT OF THE DISCLOSURE The present disclosure relates to a power system and method employing an axial gas turbine having exhaust ducts immediately adjacent to the last symmetrical blade set of the gas turbine last stage for separately collecting the outermost high-pressure exhaust gas and the innermost low-pressure exhaust gas. A transducer, preferably a steam boiler, is operatively powered by the high-pressure exhaust gases and the low-pressure exhaust gases are directly vented to the atmosphere. The ducts are positioned so that the dilference between the high and low-pressure exhaust gases is substantially equal to the friction losses within the boiler.

This application is a continuation of Ser. No. 587,496, filed on Oct. 18, 1966, now abandoned.

As is commonly known, exhaust gas from gas turbines is discharged at very high temperatures and is therefore utilized for various purposes. However, various services require the exhaust gas at different pressures depending on the kind of services. In this connection it is objectionable to derive the whole of exhaust gas at its high pressure from a single gas turbine to divert the exhaust gas for services requiring it at different pressures depending on the kind of services because this manner of exhaust gas derivation results in reduced output of the gas turbine. It is also known in the art that pressure distribution of gas turbine exhaust gas along the radial direction of the last stage movable blade can be made uniform or non-uniform as required depending on the design of the gas turbine.

It is the primary object of the present invention to provide a gas turbine exhaust chamber of improved structure which minimizes the total pressure loss of gas turbine exhaust gas and ensures a turbine operation by which the turbine exhaust gas can be most efiiciently utilized depending on the kind of services.

According to the present invention, there is provided an exhaust chamber of a gas turbine characterized by the provision of at least one partition separating said turbine exhaust chamber into a plurality of compartments which are concentric about the rotor axis, the inner end of said partition terminating at a position adjacent to the last stage movable blades of the turbine rotor so that exhaust gas portions at different pressures can be derived depending on desired services.

A preferred embodiment of the present invention will be described with reference to the accompanying drawings so that the above object, advantages and features of the invention can more clearly be understood.

In the drawings:

FIGURE 1 is a schematic diagram of a system for utilizing the exhaust gas from the exhaust chamber of the invention;

FIGURE 2 is a schematic diagram of another system for utilizing the exhaust gas from the exhaust chamber of the invention; and

FIGURE 3 is a sectional view of the exhaust chamber of the invention shown in FIGURES 1 and 2.

Referring first to FIGURE 3, there is shown a portion of a gas turbine including a rotor 1, last stage stationary blades 2, last stage movable blades 3 and an exhaust chamber 4. In the exhaust chamber 4 to which the present invention is applied, a partition 5 is provided in a manner that it separates the exhaust chamber 4 into two compartments which are concentric about the axis of the rotor 1 and its inner end terminates at a position adjacent to the last stage movable blades 3. The compartment defined close to the rotor axis is a low-pressure exhaust chamber section 6 and the compartment defined remote from the rotor axis is a high-pressure exhaust chamber section 7. These exhaust chamber sections 6 and 7 are provided with respective exhaust outlet ports 8 and 9.

When steam demand is relatively little and the entire exhaust gas need not be passed through a waste heat boiler in an exhaust gas utilization system as shown in FIGURE 1, the exhaust gas portion from the exhaust outlet port 8 is directly discharged to atmosphere through a duct 13a. On the other hand, the exhaust gas portion from the exhaust outlet port 9 is solely led through a duct 14a into a waste heat boiler 11a to be utilized for the generation of steam therein and is finally discharged to atmosphere through a waste gas duct 17a. Steam generated in the Waste heat boiler 11a is led to services by way of a steam supply conduit 15a and boiler feed water is supplied by way of a conduit 16a.

When steam demand is great and it is necessary to assist the combustion by adding fuel to a portion of the exhaust gas, a system as shown in FIGURE 2 is employed in which the exhaust gas portion from the exhaust outlet port 9 is led through a conduit 14b into the combustion chamber 18 of a waste heat boiler 11b and mixed with fuel supplied from a fuel supply conduit 19 to assist the combustion. On the other hand, the exhaust gas portion from the exhaust outlet port 8 is directly supplied through a conduit 1312 into the waste heat boiler 11b. The boiler exhaust is discharged to atmosphere by way of a waste gas conduit 17b, while boiler steam is led out by way of a conduit 15b and boiler feed water is supplied by way of a conduit 16b.

In the system shown in FIGURE 1, the pressure of the exhaust gas portion from the exhaust outlet port 9 is required to be higher than that of the exhaust gas portion from the exhaust outlet port 8 by an amount of pressure loss in the waste heat boiler 11a, which amount is of the order of to 200* millimeters in water column. On the other hand, in the system shown in FIGURE 2, the pressure of the exhaust gas portion from the exhaust outlet port 9 is required to be higher than that of the exhaust gas portion form the exhaust outlet port 8 by an amount of pressure loss in the boiler combustion chamber 18, which amount is of the order of 100 to 200 millimeters in water column. In order to give a pressure differential of 100 to 200 millimeters in water column between the exhaust gas portions derived from the exhaust outlet ports 9 and 8, design conditions may be such that the gas flow at the outlet of last stage movable blades is set at a mean flowout rate of meters per second and a velocity dilferential of 15 to 30 meters per second is maintained between the gas flows into the exhaust chamber sections 6 and 7 divided by the partition 5, assuming that static pressures at the outlet ends of the last stage movable blades are equal for both the exhaust chamber sections 6 and 7.

It will be appreciated from the foregoing description that the gas turbine exhaust chamber of the invention having a partition whose inner end terminates at a position adjacent to the last stage movable blades and which is disposed in concentrical relation with respect to the rotor axis is advantageous in that gas turbine exhaust can be utilized according to desired services and the gas turbine operation can be efiected without any reduction in the overall efiiciency of the gas turbine.

I claim:

1. A power system, comprising: an axial gas turbine having a single last stage terminal movable blade set symmetrical with respect to the turbine axis; first turbine exhaust duct means for collecting only the exhaust gases passing through and immediately adjacent the radial outermost portions of said terminal movable blade set, second turbine exhaust duct means for separately collecting only the exhaust gases passing through and immediately adjacent the radial innermost portions of said terminal movable blade set at a substantially different pressure; boiler means separate from said gas turbine for using the heat of the exhaust gases in only one of said first and second duct means to vaporize a liquid into a useful gas form; third duct means connected to said one duct means for conducting the exhaust gases only from said one duct means to said boiler means.

2. The power system according to claim 1, wherein the other of said first and second duct means is in direct fiuid communication with the atmosphere.

3. The power system according to claim 2, wherein said one duct means is the high-pressure duct containing the high-pressure exhaust gases, said boiler means including passage means for conducting said high-pressure gases through said boiler and discharging them directly to the atmosphere, and said exhaust duct means providing a pressure differential between said first and second duct means that is substantially equal to the pressure drop in said high-pressure exhaust gases passing through said boiler.

4. The method of converting hot high-pressure combustion gases into useful work within a gas turbine having a single last stage terminal movable blade set symmetrical with respect to the turbine axis and into useful vapor energy in a boiler utilizing the heat of hot gases for converting a liquid into a useful vapor, comprising the steps of: providing high-pressure combustion gases; moving the high-pressure combustion gases through the gas turbine to produce useful work; removing only an annular portion of the turbine exhaust gases concentric with the turbine axis from the last stage terminal movable blade set at one pressure; conducting said exhaust gas portion to the boiler; utilizing said exhaust gas portion in said boiler to vaporize a liquid into a vapor separate from said exhaust gases.

5. The method of claim 4, including the steps of providing the boiler with a combustion chamber; removing a different annular portion of the turbine exhaust gases concentric with the turbine axis from the last stage terminal movable blade set at a substantially different higher pressure; conducting the higher pressure portion of said exhaust gases into the boiler combustion chamber.

References Cited UNITED STATES PATENTS 696,867 4/ 1902 Fullager. 1,320,671 11/1919 Baumann -64 1,375,075 4/1921 Baumann. 2,650,666 9/1953 Dorand et al. 135.4

FOREIGN PATENTS 847,018 6/ 1939 France.

1,338,515 8/1963 'France.

EVERETTE A. POWELL, 1a., Primary Examiner.

U.S. DEPARTMENT OF COMMERCE PATENT OFFICE Washington, 0.0. 20231 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,400,911 September 10, 1968 Hideo Kojima It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading to the printed specification, between lines 7 and 8 insert Claims priority, application Japan, Oct. 25,

Signed and sealed this 3rd day of February 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Attesting Officer Commissioner of Patents WILLIAM E. SCHUYLER, JR. 

